One of our Linux (CentOS 7.5) servers got unreachable sometimes.
The only solution what i have is systemctl restart network
.
And I found the fact that I could not ping any outside hosts and vice versa.
So I replaced the server with new server to solve this problem but i got the same problem on new server. (But another interface for our private network always reachable.)
network detail:
$ ifconfig
docker0: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500
inet 172.17.0.1 netmask 255.255.0.0 broadcast 172.17.255.255
inet6 prefixlen 64 scopeid 0x20<link>
ether txqueuelen 0 (Ethernet)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 8 bytes 656 (656.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
em1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet xxx.xxx.178.235 netmask 255.255.255.192 broadcast xxx.xxx.178.255
inet6 prefixlen 64 scopeid 0x20<link>
ether txqueuelen 1000 (Ethernet)
RX packets 36757565 bytes 32443194055 (30.2 GiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 38804620 bytes 32581348506 (30.3 GiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
device interrupt 53
em2: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.1.11 netmask 255.255.255.0 broadcast 192.168.1.255
inet6 prefixlen 64 scopeid 0x20<link>
ether txqueuelen 1000 (Ethernet)
RX packets 4123332 bytes 1311703055 (1.2 GiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 3546248 bytes 510328190 (486.6 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
device interrupt 54
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
inet6 ::1 prefixlen 128 scopeid 0x10<host>
loop txqueuelen 1000 (Local Loopback)
RX packets 69896787 bytes 31178480745 (29.0 GiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 69896787 bytes 31178480745 (29.0 GiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
System logs are surprisingly clear.
Any log files seem to indicate no error except for errors due to network stopped.
Please let me know the best steps to find out problem. I have no clue anymore.